The solar system’s innermost planet finally has its very own orbiter, in the form of NASA’s MESSENGER spacecraft (the acronym-makers at NASA must be very proud of that name – it’s short for “MErcury Surface, Space ENvironment, GEochemistry, and Ranging”, and MESSENGER itself is also a riff on Mercury’s mythical as the fleet-footed messenger of the gods. Cunning!).

Today, on 29th March 2001, it sent back its first image from Mercury orbit – which is exactly 37 years after Mariner 10 sent back its first pictures of Mercury after it first flew past (but didn’t go into orbit around) the planet in 1974!

The first (colour) image from Mercury Orbit! Credit:NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

As you can see, Mercury looks very moon-like (I think it looks vaguely reminiscent of the far sde of the moon myself), though there are differences – there are no dark maria, for example, and Mercury is somewhat larger and a lot denser than our Moon. The bright ray crater visible in the image is called Debussy (Craters on Mercury are named after “deceased artists, musicians, painters, and authors who have made outstanding or fundamental contributions to their field and have been recognized as historically significant art figures for more than 50 years”), and the bottom part of the image reveals cratered terrain that we’ve never seen before!

This is only the beginning – over the next year MESSENGER is going to be taking thousands of high resolution images of the surface and gathering data that will revolutionise our knowledge of the smallest planet in the solar system, as well as helping to answer long-held questions about the formation and evolution of the solar system. Hopefully we’ll be hearing about some very exciting results from the data in the next few months!